[ADI] allow clearing all experiments at once

If the package name is not specified in the
`clear-developer-verificationn-result` command, clear all experiments at
once.

BUG: 399436145
Test: manually
FLAG: android.content.pm.verification_service

Change-Id: Ie2e73d1815282b48cec8f81e85f10e7dccec5cc7